01 - Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper and lightly grease with butter or oil.
02 - In a large mixing bowl, whisk together all-purpose flour, baking powder, baking soda, salt, and ground cinnamon until evenly blended.
03 - In a separate bowl, whisk eggs, buttermilk, melted unsalted butter, vegetable oil, granulated sugar, light brown sugar, and vanilla extract until the mixture is smooth.
04 - Pour the wet ingredient mixture into the dry ingredients. Stir gently just until combined. Avoid overmixing to maintain a tender texture.
05 - Spread the batter evenly into the prepared baking pan.
06 - In a small bowl, beat softened cream cheese, ranch dressing, buffalo sauce, and powdered sugar with an electric mixer until smooth. Dollop spoonfuls over the batter and gently swirl with a knife to create a marbled pattern.
07 - Bake in the preheated oven for 22 to 25 minutes, or until the bars are golden on top and set in the center.
08 - While bars are still warm, brush the surface with melted unsalted butter. Mix granulated sugar and ground cinnamon, then sprinkle generously over the top.
09 - Allow bars to cool in the pan for 10 to 15 minutes. Cut into 12 portions and serve while warm or at room temperature.